Numerous instruments for the measurement of radiation within the microwave and infrared frequency range of the electromagnetic radiation spectrum are known. Infrared responsive instruments include transducers such as thermocouples, Golay cells, photoconductors and the like, for transforming said infrared energy to a more directly useful form. Such transducers, however, are inefficient and are of low sensitivity and large bandwidth in the relatively low energy infrared frequency range. In the microwave region, paramagnetic amplifiers often are used for amplification of low microwave signals for subsequent detection. The sensitivity of such prior art microwave and infrared detecting arrangements does not approach that obtained with the present invention in which direct counting of photons in the infrared and microwave frequency range is possible.